Looks like this is just because kernel.config says:
# CONFIG_IP_NF_NAT_LOCAL is not set
and ip_nat_rule does:
#ifndef CONFIG_IP_NF_NAT_LOCAL
if (hook_mask & (1 << NF_IP_LOCAL_OUT)) {
DEBUGP("DNAT: CONFIG_IP_NF_NAT_LOCAL not enabled\n");
return 0;
}
#endif
but why is this feature disabled by default?